The OpenAPC initiative releases data sets on fees paid for open access journal articles by universities and research institutions under an open database license. OpenAPC is operated by Bielefeld University Library.
Main place for OpenAPC to collect and maintain its data is GitHub, where all core data files are kept and redacted in CSV format. This site and its open backend were established to improve accessibility and re-use of the data, which means that there are 3 ways to access the OpenAPC data sets, differing in their tradeoff between flexibility and ease of handling:
The most basic way to access the Open APC data is the main APC file on GitHub. It is a CSV file, meaning that it should be easily processable by a wide range of tools and programming languages. A schema description of the file can be found here.
Since the raw CSV data can be difficult to analyze without tool support, a more elegant method is querying the OpenAPC OLAP Server. This service implements an online analytical processing framework based on cubes, forming the backend of treemaps.openapc.net. For usage instructions have a look at this HOWTO.
The treemaps on this site present the most easy and intutitive way to browse and inspect the OpenAPC data. It is possible to either view the data for single institutions or the whole data set.